Occupational asthma

Last reviewed: 21 Aug 2021

Last updated: 04 Sep 2018

Should be suspected in all adult patients with asthma.

An occupational history should be taken to identify work-related causes. Details of work exposures should be obtained from material safety data sheets and other material available to the patient from their workplace.

Objective evidence of asthma should be obtained from spirometry, a bronchodilator response, and/or a methacholine challenge. Tests should be performed when the patient is symptomatic and/or within days of having exposure to a suspected etiologic agent.

If sensitizer-induced occupational asthma is suspected, additional testing of asthma should be done, preferably while the patient is still working. Whenever possible an immunologic response to a suspected work sensitizer should be demonstrated by skin or in vitro tests.

Where possible, an early diagnosis based on as much objective data as is available should be made.

In sensitizer-induced occupational asthma, removal from any further exposure to that agent should be recommended.

In irritant-induced occupational asthma, preventive measures should be implemented in the workplace to reduce future exposures and episodes.

For all causes of occupational asthma, the clinician should continue treating the asthma as appropriate, assist in the initiation of any appropriate compensation claim, and consider other workers at risk.

Definition

Occupational asthma (OA) is asthma caused by the workplace and may result from immunologic or nonimmunologic stimuli.[1] There are 2 main forms. Sensitizer-induced OA is caused by immunologic stimuli and develops after a latency period between first exposure and the onset of symptoms.[2][3] Irritant-induced OA (including reactive airways dysfunction syndrome) is caused by nonimmunologic stimuli.[4]

History and exam

Key diagnostic factors

occupational exposure to sensitizing agents or irritants
symptoms of asthma that improve during holidays
initial onset of asthma symptoms during a work period

More key diagnostic factors

Risk factors

high-level exposure to sensitizer
atopy
genetic factors
smoking

More risk factors

Diagnostic investigations

1st investigations to order

spirometry (pre- and post-bronchodilator)
chest x-ray
skin prick testing
specific serum IgE assay
nonspecific bronchial provocation testing
serial peak expiratory flow rate

More 1st investigations to order

Investigations to consider

specific inhalation challenge

More investigations to consider

Emerging tests

induced sputum cytology
exhaled nitric oxide

More emerging tests

Treatment algorithm

ACUTE

sensitizer-induced

irritant-induced

ONGOING

symptomatic asthma

Contributors

Authors

Ryan Hoy, MB BS, MOEH, FRACP

Respiratory Physician

The Alfred Hospital

Melbourne

Victoria

Australia

Disclosures

RH declares that he has no competing interests.

Susan M. Tarlo, MB BS FRCP(C)

Professor of Medicine

University of Toronto

Respiratory Physician

Toronto Western Hospital

Toronto

Ontario

Canada

Disclosures

SMT has performed medical assessments of patients at the request of the Ontario Workplace Safety and Insurance Board (the Ontario workers' compensation system), for which payments were made to her institution. She has also received research grant support from the Ontario Workplace Safety and Insurance Board.

Peer reviewers

Ware Kuschner, MD

Associate Professor of Medicine

Stanford University

Stanford

Staff Physician

US Department of Veterans Affairs

Palo Alto Health Care System

Palo Alto

Disclosures

WK declares that he has no competing interests.

Karin Pacheco, MD

Associate Professor of Medicine

National Jewish Medical Centre

Denver

Disclosures

KP declares that she has no competing interests.

Philip Harber, MD

Professor of Medicine

University of California

Los Angeles

Disclosures

PH declares that he has no competing interests.

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